Automatic telephone system



J. ERICKSON AUTOMATIC TELEPHONE SYSTEM April 20 1926. 1,581,309

Filed March 13 1905 ll Sheets-Sheet 1 J. ERICKSON AUTOMATIC TELEPHONE SYSTEM ll Sheets-Sheet 3 Filed March 13, 190E E M Wu April 20, 1926.

J. ERICKSON AUTOMATIC TELEPHONE SYSTEM I ll Sheets-Sheet 5 Filed March 15, 1905 April 20 1926.

J. ERICKSON AUTOMATIC TELEPHONE SYSTEM Filed March 15 1905 ll Sheets-Sheet 8 gwam.-

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J. ERLCKSON AUTOMATIC TELEPHONE SYSTEM 1905 ll Sheets-Sheet 9 h m h m w$ if. w I 1 mmw .H I M Y H I a Filed March 13,

April 20, 1926.

J. ERICKSON AUTOMATIC TELEPHONE SYSTEM 1905 11 Sheets-Sheet 11 Filed March 13,

Ina [971607- Patented Apr. 20, 1926.

UNI-TEDST-ATES PATENT OFFICE.

JOHN ERICKSON, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, '10 AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

AU'romrIc 'rnmrno m sYs'rml.

Application filed larch 13, 1905. Serial No. 249,709.

T 0 all whom it may concern:

Be it known that I. JOHN ERICKSON, a citizen of the United States of America, and resident of Chicago, Cook County, Illinois, have invented a certain new and useful Improvement in Automatic Telephone Systems, of which the following is a specification.

My invention relates to automatic telephone systems in general, but more particularly to-systems of that character in which any subscriber may, through the medium'of suitable selective apparatus, establish connection with the line of any other subscriber of the system, providing, of course, that such line is not busy, and especially to automatic telephone systems in which the mechanism or apparatus by which one subscriber makes connection with another siibscribers line, without the aid of a telephone operator or other attendant, consists of a suitable number of switches which operate on the stepby-step principle and which are. by reason of the provision of suitable switching apparatus at the subscribers stations, under the control of, and adapted to be operated by, the diilereiit subscribers.

Prior to my invention, it has been the general practice, so far as I am aware, to employ. in a telephone system of the above pi-irticular character, either a number of switchescorresponding in number to the total number of subscribers. each of said switches being allotted and individual to a single subscriber, and each switch thusbeinguscd only by the. subscriber to whom it is allotted in establishing connection, either directly or indirectly, with the line of some other subscribm', or one or more constantly operating switches for picking up calls, These individual switches. if adapted to receive the llll])lll5"( or impulses corresponding to the first digit of the called number, are known as lirst selectors, provided, of course, that the exchange is ot-such size as to necessitate the use of a plurality of switches in establishing connection between two subscribers lines. Again, it has been proposed to reduce the number of said first selectors to a percentage basis that is to say, to employ, for example,.only ten or twenty so-called first selectors for each one hundred subscribers in the exchange, each group of selectors thereby being com: mon to alarger numberof subscribers; and

with an arrangement of this character it lhas been the practice to then provide each subscriber with a so-called individual-switch adapted to be operated by one or more impulses projected by the subscriber over the line preliminary to calling the number-0t the desired subscriber. Other more or less similar constructions and arrangements have been proposed, the object being generally to reduce the number of switches in the exchange as niuch as possible; but in each case, so far as I am aware, it has always been necessary,.prior to my invention either to employ constantly operating switches, or

to provide each subscriber with an individ-' ual selective switching device of some character.that is to say, the number of stepbystep or other suitable selective switching devices, through the medium of which any subscriber makes the initial connection necessary in establishing connection with any other subscribers line, always corresponding to the total number of subscribers sta-v tions having connection with the exchange or central station. In other words, and regardless of the arrangement and division .of the switching devices, it has always been necessary, prior to my .1nvent1on,either to employ constantly operating switches, or to provide each telephone subscriber with some sort of a selective switchingvdevice, that is,

a trunk-selecting or line-connecting device. For example, in my prior application, Serial No. 249,499, filed.

individual to his line.

by me on the tenth day of March,,1905, for improvements in automatic electrical switching means, there is a switch-operating machine common to all of the members of a group of subscribers, each subscriber, however, being provided with an individualswitchthat is to say, a step-by-step switching device which is allotted to a subscribers line and used only by that subscribeiz although all of the different individualswitehes are operated tl'irough the medium of a switch-operating machine which is common to all of the subscribers iii the group;

but in the present case, as will hereinafter more fully appear, one of the principal objects to be attained is the reduction of all step-by-step switches to a percentage basis. so as to materially reduce the amount of switching machinery and apparatus necessary for service between the subscribers, and

whereby practically none of the devices in" the central stat on or exchange are individual to the subscribers lines except, perhaps, in the matter of line-relays or other similar extremely simple controlling devices, as will hereinafter more fully appear; and the dispensing with all constantly operating switches or circuit-controlling machinery.

Generally stated, therefore, the object of my invention is to provide such an improved.

construction and arrangement as will afford satisfactory and cilicient telephone service between the different subscribers, but without the necessity of providing each subscriber with an individual selective switching device, and with the further advantage of a material reduction in the amount of apparatus or selective switching devices necessarily employed at the exchange or central station.

A special object is to provide an improved construction and arrangement involving a selective switching apparatus'which may be used in common by a group of subscribers of any suitable number, and which, after serving the purpose of one subscriber in mak ng the first connection necessary in establishing connection with some other subscribers line, will then automatically place itself in such condition as to be in readiness for use by the next subscriber of the group desiring to call some other subscriber, the time required by the said apparatus in establishing the desired connection being of such short duration that it can, even though the ditterent Subscribers of the group send in calls in rapid succession, always attend to the wants of each subscriber, it being extremely unlikely that any two subscribers will simultaneously take down their receivers and attempt to use the said apparatus at the same time.

Another object is to provide an improved construction and arrangement whereby a selective switching apparatus may be used in common by a number of subscribers as the means for making the first connection neccssarv in establishing connection with the called subscriber, and in combination with a group of first selectors considerably less in number than the group of subscribers to whom the apparatus as a whole is allotted, it being possible with this arrangement to employ, for example, only ten first selectors for each one hundred subscribers, the said selective switching apparatus which is common to the one hundred subscribers being adapted to swit h a calling subscribers line to any one of the said ten first selectors, the selector thus picked out being, of course, one that is not then in use by another subscriber of the same group.

A further object is to provide an improved normally at rest trunk selecting and connect ing apparatus interposed between the subscribers lines and the first-selectors or other suitable means for making connections in accordance with the called number.

It is also an object, of course, to provide certain details and features of construction tending to increase the general efficiency, economy of installation and maintenance, and serviceability of an automatic telephone system of this particular character.

In many respects, my present invention constitutes a matter of improvement over or upon the telephone system and devices disclosed in my said prior application. For example, in my said prior application Fshow an arrangement by which a single switch operating machine may be made common to all of the members of a group of susbcribers,

and by which this machine. may be ci'nployed' by any subscriber in such group as a means for operating one of a number of step-bystep switches, so as'to connect the calling subscribers line with a trunk-line, and without interfering with the subsequent and practically immediate use of the said machine by other subscribers for establishing other connections while the operated switch remains in use; but with the arrangement hereinafter described and claimed, the switches which are operated automatically by the switch-operating machine, instead of being each individual to a subscriber, are considerably less in number than the total number of subscribers and are, furthermore, electrically connected with the said switchoperating machine, instead of being connected mechanically therewith, as in my said prior application. Consequently, as previously stated, one advantage of my present invention resides in the fact that practically none of the devices in the exchange are individual to the diil'ercnt subscribers, each stcp-by-step switch, or other switching device capable of making any one of a number of possible connections, being common to a plurality of subscribers, and nothing ex cept the number of line-relays, or other similar simple devices. being the same in number as the total number of subscribers.

In the accompanying drawings, Fig. l is a diagrammatic view illustrating the electrical construction and circuit arrangement of the said selective switching device which is common to the said group of one hundred subscribers, more or less.

Fig. 2 is a diagrammatic view illustrating the electri'al construction and circuit arrangement of one of the pi-climiuary-con ncctors which are arranged in groups of ten, more or less, and arch group being allotted to a group of one hundred Subscribers, more or less. 1

Fig. 3 is a plan view of the machine or switching apparatus illustrated diagrammatically in Fig. 1. and showing also several of the line" or individual relays.

Fig. i is an end elevation of the selective switching device shown in Fig. 3.

Fig. 5 is a section on line 55 in Fig. 3,

looking in the direction indicated by the arrows. 1

Fig. 6 is a detail showing a different position of some of the parts shown in Fig.- 5.

Fig. '7 is a detail section on line 77 in Fig. 4.

Fig. 8 is a horizontal section on line 5-5 in Fig. 3, but looking in a direction opposite to that indicated by the arrows.

Fig. 9 is another end elevation of the selective switching device shown in Fig. 3.

Fig. 10 is a detail section on line 1010 in S.

Fig. 11 is a detail perspective of one of the spring-switch devices involved in the construction of the said selective switching 'devicc. i

Fig. 12 is a diagrammatic representation of a subscrrhers telephone and switching outfit. I

Fig. 13 illustrates the mechanical construction of one of the preliminary-com net-tors which constitute a new feature in an automatic telephone system.

Fig. 14 illustrates an ordinary connectorswitch", the same being adapted for use in making the. final connection with the called subscribefs line. and which is herein shown, described and claimed in combination with other Features, but which in itself" is not llCVV.

Fig. 15 is a diagram illustrating the circuit. connections existing during the time two subscribers lines are connected up for conversation in a system in which it is assumed that only a comparatively small number 0t subscribers are involved, and in which no first. second or third selectors are employed. an ordinary connector being sullicicnt tor the requirements of the calling subscriber at't er the preliminary connections have been made.

Fig. 16 is an enlarged detail view of one of the series of relays shown in Fig. 1.

Fig. 17 is a diagram showing the capacity of the system increased, say from a one hundred to a one thousand system. In this figure the trunk conductors LL leading from the wipers of the preliminary-connector or non-numerical selector terminate in a selectorswitch" N. instead of in a connector as in Fig. 15. The selector N is of the general type described in United States Patent No. 815321, granted March 1?, 1906. to Keith. Erickson & Erickson. From each set of bank-contacts of this selector a trunk line leads oil'. which terminates in a comrector-switch such as the one shown in Fig. 15. One of these trunk lines is shown comprising the conductors L and 1. In other words. the selector N is properly inserted (in Fig. 15) between the trunk-connecting switch and the connector.

Fig. '18 shows diagrammatically a second selector which, if the system is still further increased in capacity, as from one-thousand to ten-thousand, is inserted between the first selector'N and the connector-switch".

Fig. 19 shows diagrammatically a third selector-switch which is used when the central otiice is arranged for a one-hundredthousand system. The selector 0 is shown connected with the connector-switch M, which is the same as the connector shown in Fig. 15.

As thus illustrated, and with a view to a more general understanding of the construction and operation of my improved automatic telephone system, before going into a more thorough description of the details of the construction, the arrangement and mode of operation are as follows: The subscribers may be divided into groups of one hundred each. Each subscriber may be provided with any suitable kind of apparatus, such, for example, as shown in Fig. 12. Each subscribers line terminates at the exchange or central station in a line-relay, such. for example, as the line-relay shown at the right in Fig. 2. At the. central station each line is also preferably normally connected with the bank-contacts of a suitable number of automatic switches, say ten, of the step-by-step switches shown at the left in Fig. 2. In addition, an automatic switching device. of the character shown in' Fig. 1 is allotted to each group of subscribers and associated with the ten stepby-step switches shown in Fig. 2. Then the subscriber starts to call another subscriber, the act of removing the receiver operates the line-relay at which the line of the calling subscriber terminates. This, of course, precedes the operation of calling the number of the desired subscriber, and all occurs in the interval between the removal of the calling subscribers receiver and the transmission of the first impulse or impulses necessary to calling the desired number. As soon as the line-relay operates, it throws the apparatus shown in Fig. 1 into operation, and from then on until the subscriber begins calling the desired number, the

operation isstrictly automatic. As soon as the automatic switchingdevice shown in Fig. 1. started by any one of the subscribers in the group to which this switch is allotted, it automatically picks out an idle member of the group of ten step-by-stcp s\.'itches-that is to say. the ten step-by-stop switches or the character shown in Fig. 2, and which are allotted to the aforesaid group of one hundred subscribers. and to the switching apparatus shown in Fig. 1. The arrange ment is also such that the switch shown in Fig. 1 is preferably always connected up with one of the switches shown in Fig. 2* that is to say, with one of the ten switches which is not. busy. Consequently, the apparat'us shown in Fig. 1, as soon as set in motion, automatically calls the number of the calling subscriber. In other words, the switch shown in Fig. 1 automatically transmits impulses corresponding to the number of the calling subscriber, causing the switch in Fig. 2 to select the bank-contacts connected with the calling subscribeus line. In this way, the calling subscriber, by simply removing the receiver, or in any other suitable way, automatically calls his own line, so to speak. and thereby establishes connection with an idle trunk-liue running to a so-called .tirst selector, for example, or to some other switch. As soon as this has been done, the subscriber is then, and by that time. ready to begin the operation of calling the desired number: but he is only connected with the said first selector, or other switch, from the time he begins making the call until the conversation is terminated and the switches restored to their normal positions. Thus there are no individual-switches, the line-relays being practically the only devices which are each made individual to a single subscriber. Obviously, therefore, the number of so-called first selectors, and other necessary switches, may be consider ably loss in number than the total number of subscribers. and with the result that the apparatus is simplified and materially reduced without in any way reducing the cllicicncy oi service between subscribers. This, of course, largely due to the fact that the auton'iatic switch shown in Fig. 1, at'ter automatically calling the number of the calling subscriber, and thereby establishing connection between the calling subscriber-s line and one of the ten switches shown in Fig. 2. then returns to its normal condition and remains in readiness for use by another subscriber of the same group. \Vith this arrangement, therefore, the switch shown in Fig. 1 is, unless two subscribers of the group to which it is allotted simultaneously take down their receii'ers, etc., which is extremely unlikely, always in readiness to be en'iployed by any subscriber ot the group for the purpose of connecting his line with an idle first selector. Thus, notwithstamliug the fact that there are no step-by-step selective switches which are individual to the. subscribers, the operation, as far as the calling subscriber is concerned, is practically the same as if each line terminated in a. so-called first selector or other similar switch. In other words. the calling subscriber, by simply removing his receiver from the usual switch-hook, automatically starts a train of electrical steps or operations which are completed by the time he is ready to begin calling the desired number; and, without any hesitation or additional work on the part of the calling subscriber, a first selector, a connector, or other switch,

according to the size of the exchange, is thus placed in electrical communication with his line and in readiness to recelve the impulse or impulses corresponding to one or more digits of the called number, as the case may time of taking down the calling subscribers receiver and the consequent automatic connection with an idle first selector, or other switch: and the devices then used for calling the desired number, and for completing the connection through to the called subscribers line, may be of any suitable, known or ap proved character.

In a general way, and before describing the details of construction, the operation of connecting up one subscribers line with another is as follows: Suppose, for example, that the subscriber at station A (Fig. 15) and whose number may be assumed is 51, desires to converse with the subscriber at station B, it being assumed that the latters number is 99, and also that, as a matter of convenience of illustration, the two subscribers belong to the same group to which the I)reviously mentioned switch-operating machine is allotted; although, of course, it will be understood that the exchange may be. of any suitable or desirable size, the. only difference, in a general way, between one of one hundred subscribers and one of, say, ten thousand subscribers being with respect to the number of automatic switches which any given subscriber must employ in connecting his line with the line of some other subscriber. \Vith the arrangement shown, however, subscriber 51, in removing his receiver from the switch-hook a, will thereby produce a momentary engagement of the switch-hook projection a with the switchconstanta (Fig. 12). This, it will be seen, mon'ientarily grounds the subscribers lineconductor Z, the grounded circuit thus mo mentarily formed including this line-com ductor, the conductors a, a the said switchhook, the contact a the conductor a, the contacts a", (1. to ground at a In this way, the removal of the receiver momentarily grounds one. side of the calling subscribcrs line, with the result that the rclaycoil 7 (Fig. which is one of the two relay-coils 6 and 7-norn1ally bridged across the subscribeus line. and normally connected at the middle point with contacts 8, 9 and 10, the latter being connected with a non-grounded pole of battery 11is energized sufliciently to attract the armature 12. In other words. the momentary grounding of the subscribers line completes a temporary grounded circuit including the coil 7, and including the battery 11. hen

thus energized, the subscribers line-relay, by altrzu-ting its armature 12, causes the nornially-separateil contacts 3, 4 and '5 to be brought into engagement with each other, it being seen that contact 5 is connected to ground (Fig. 1). This, it will be seen, completes a circuit from ground through contact 3'ot' conductor 17 to relay-coil 15-, thence over conductor 19, contact-arm 24, contactarm 21, relay-coil 25. conductor 26 to the non-grounded pole of battery 11, and thence to ground again. In this way, the energizing of the subscriber's line-relay is instantly followed by the energizing of the inner relay-coil 15, causingthis relay to attract its armature. and by the energizing of relay 25. which latter also attracts its armature. Simultaneously with the formation of these circuits and the energizing of these relays, however, another circuit is closed from ground through contact-arm 1 to conductor 18, thence over inner relay-coil 16, over conductor 1 through contact-arms 24 and 21, through relay-coil 25, and over conductor 26 to battery 11 and thence to ground. Obviously, with the arrangement shown, the inner relay-coil 16 when energized will cause its armature 14 to break contact with the contact-point 27, and the inner relay-coil 15. when. energized as described, attracts its armature 13, thereby causing the latter to break contact with the contacbpoint 28. At the same time, the energizing of relay-coil '25 will cause'its armature to engage the contact-point 30, thus closing a circuit as follows: Fro-m battery 11 through conductor 26, through contacts 3O an l,29. through rotary-magnetcoil 31, thence through normally-engaging circuit-breaking contacts and 32 to ground and back to battery. This rotarymagnet, when thus energized, attracts its arn'iature 135", causing the latter to separate the contacts 32 and 33, and thereby permitting the armature to be instantly released. As will hereinafter more fully appear, the construction of the said rotarymagnet is such that each time its armature is released it causes its pawl to engage a tooth of the ratchet-wheel on the switchsha'i't, to which latter is attached a Springwiper or contact-brush 35. the latter resting normally on a series of contact-teeth or S\.'lt('.ll-C0lll'i1(fl'$ arranged in a circle. Consequently, and as the armature 135 is alternately attracted and released, owing to the rapid make-and-break action which it produces in the coil 31,. the spring-wiper 35 is given a rapid step-by-Step motion over the said contact-teeth or switch-contacts. The spring-wiper 35 is, as shown in Fig. 1, included in a circuit. and as it makes the first rotary step the cam 34. which is attached to the same shaft. breaks contact with the spring 21, thereby allowing thelatter to spool or magnet, and thence through all the corresponding coils of the other sixteen magnets shown in Fig. 1, through eonduetor 38, contacts 20 and 21, coil 25, conductor 26 to battery 11 and thence to' ground. Preferably, the windings 36, 37, &c., throughout all of the eighteen magnets, these windings being connected in series, are of such construction that the attractive power of their cores or pole-pieces is comparatively slight; so that armatures 1 1 and 13, which are, it will be remembered, already in contact with their respective polepieces or magnet-cores, will beretained in contact therewith; but none of the armatures of the sixteen relay-magnets will be attracted. The armature 29 of rclay25 will, however, be retained in contact with its pole-piece or magnet-core, thus maintaining the continuity of the previously closed cir-' cuit through rotary-magnet 31 and its circuit-breaking contacts 32 and 33; and in this way, the said rotary-magnet will continue to rotate its shaft, and thereby keep the spring-wiper 35 moving until the latter has made a complete revolution. It will be seen, of course, that. the cam 34 will also make a complete revolution simultaneously with the said wiper, and will, as it returns to its starting point, again make contact with contact-arm 21, thus pressing the latter out of engagement with contact-arm 20, and again closing contact with the arm or spring 24-; and this breaks the circuit just described from ground through windings 36, 37, &c. in series through the. other series relaywindings, through conductor 38, contacts 20 and 21, relay-coil 25, conductor 26 to battery and to ground. Instantly, upon the break- I ing of this circuit, relay-coil 25 will allow its armature to return to normal position, thus breaking contact between said armature 29 and the contact 30, and thereby opening the circuit through rotary-magnet 31. At the same time, however, the said armature 14. of relay-coil 16 will return to its normal position in engagement with contact-point 27 and armature 13 of relay 15 will return to normal position in engagement with contact-point 28. Obviously, however, and dur ing the time that the spring-wiper 35 is making its revolution from starting point on contact 100, certain other operations will take place; and with respect to these additionalelectrical actions and operations, the

followin preliminary explanation is made: For example, the wipers or switcl'i-arms 101, [0:2 and 103, shown in Fig. 1, are diagrammatic rcprcscntatiiins of the Spring-wipers shown in Figs. 3 and 1, and hereinafter more fully described. These spring-wipers are mounted on a ditl'erent shaft from the one on which the previously described spring is mounted; but this second shaft is also rotated. in a step-b v-step manner, by means of the rotaryanagnct 104 and its armature 107, which are shown in Figs. 1, 3 and 4. This rotary-magnet 104. actuates, tlirough the medium of its armature, a pawl and ratchet mechanism similar to that actuated by the rotairy-magnet 31. Coi'iscqucntly, each time armature 107 is drawn down against its pole-piece or core, the pawl is drawn back sutlicii' ntly to engage a fresh tooth on the ratchet -whcel, and as the arnia ture is then releascd, the spring tension is such that the pawl pushes the ratchetwheel forward or around until it strikes against the stopscrew'lOS. The adjustment and location of the stop screw 108 is preferably such that when the pawl rests against it, the ratchet-wheel, together with the shaft, is locked in such a position that the springwipers 101, 102 and 103 rest in contact with one of the ten sets of contact-teeth arranged in semi-circle, as shown in Fig. 1. The method of fastening these wipers to the shaft, and of insulating them from each other, is shown in Fig. 7, and will be hereinafter more fully described.

Returning now to Figs. 1, 2 and 13, it will be seen that the ten sets of contact-teeth, such as set 102), 113 and 117; set 110, 11 1 and 118; set 111, 115 and 119, &c., are each connected with one of the ten automatic pie liininary-connectors shown at the left in Fig. 2, and previously referred to. F or convenience of illustration, only one set of these different connections is shown. The contact-point 109 is shown connected with the conductor 121; contact-point 113 with conductor 122; and contact 117 with conductor 123. These three conductors lead to the so-called preliminary-connector, or other suitable automatic switch, shown in Fig. 2, this so-called preliminary-connector being equipped only with vertical and rotar magnets 14 1 and 145, together with a release-ma, net, and, of course, with armatures, pawls, stops, etc., suitable for giving the shaft a step-by-step vertical motion and a step'bystep rotary motion. As shown, the arrangement of circuits is such that spring-wipers 101, 102 and 103 will never rest, except for a brief instant, on a set of contacts connected with a preliminary-connector which is busy or already in use; and the circuits and means which prevent these wipers from stopping on a set of busy contacts are as follows: Suppose, for example, that these wip ers 101, 102 and 103 should, for any reason whatever, he moved about and so adjusted that wiper 101 would engage contact-point 109, wiper 102 in engagement with contact 113, and wiper 103 in engagement with contact 117, it being understood that these three cont-acts constitute one of the ten ssts of contacts involved in the construction of the bank and switch-contacts shown in Fig. 4; and also assume, or the purposes of this illustration, that the preliminary-connector K, shown in Figs. 2 and 11-3 (which is the particular preliminary-conuector connected with these three bank-cmitacts) should be found busy. In such case, the spring-contact-arin 124 of the said prelimi nary-eonnectofl will rest against the contact-point 125, thus closing connectioi'i between ground and contact 109 by means of conductor 121, and thereby establishing a guarding potential at contact-point 100 by reason of its ten'iporary connection with the grounded pole of the battery or other source of current. Consequently, when the wiper 101 engages contact'point 100, a circuit will be closed from ground through conductor 121, through contact-point 109, springwiper 101, conductor 126, contact-arms 106 and 105, and through coil 101 to battery and to ground; and this will cause the retary-magnet-coil 101 to attract its armature and, by means already described, induce the shaft to which spring-wipers 101,' 102 and 103 are attached to instantly make one rotary step, thereby carrying these wipers out of contact with points 100, 113 and 117, and into contact with points 110, 114 and 118. If these last-mentioncd bank-contacts should be found busy, then the operations just described would be instantly repeated, so as to carry the spring-wipers to another position. However, in order that a better understanding of the circuits may be had, it may be assumed that when the operator or subscriber at telephone 51 starts to make the call, thus causing spring-wiper 35 to make a complete revolution over its contact points, as already described, the wiper 101 is at such time resting upon contact-point 109; wiper 102 on eontact-point 113; and wiper 103 on contact-point 117; that the preliminary-connector-switch K is in its normal position and ready to receive a call from the switch-operating machine shown in Fig. 1. if these conditions prevail at the time the calling subscriber takes down his receiver, thereby causing wiper 35 to make a complete revolution over its bank-contacts-all of which is, of course, accomplished in an instant of time--the following operations will then talte place: It will be remembered that when spring-wiper 35 moves from contact-point 100, cam 34- then moves away from contact-arm 21, thereby -permitting contact-arm 22 to engage contact-arm 23. As soon as this occurs, a circuit will be closed from ground through conretain the latter in its attracted position until spring-wiper 35 has completed its revolutimi, and thus permitting cam 341 to again come in contact with arm 21, and thereby open the circuit between contact arms 22 and 23. \Vhen this takes place, the rotary-magnet 10-1 releases its armature; then by means of the pawl and ratchet device already described, and hereinafter more fully explained. the spring-wipers 101, 102 and 103 will be moved forward one step, and onto contact-points 110, 114 and 118, so as to be ready for the next call sent in from the switch-operating machine; but these,

wipers will, of course, remain on contactpoints 100, 113 and 117 during the time that spring-wiper 35 is making its revolution. Obviously, as spring-wiper 35 is given a step-by-step motion over its contact-points 100, 131, 1.32, 133, etc. throughout the sets of contacts in the bank, and just at the time when it rests on each new contact-point, it is connected to ground through conductor 131*, contact-arm 33 and contact-arm 32. This, it will be seen, is for the reason that whenever the wiper 35 rests on a contactpoint, armature 135 is away from the core or pole-piece of its magnet; and each time armature 135 is drawn up against its core or pole-piece, contact is thereby broken between arms 33 and 32, the result being that contact-arm or wiper 35, as it is stepped over its teeth, will also momentarily be connected to ground as it rests on each tooth in itspath of travel. The effect of this action will be readily understood; for as contactarm or wiper 35 rests on contact-point 131, a circuit will thereby be closed from ground through contact-arm 32, contact-arm 33, conductor 134 contact-arm or wiper 35,

contact-point 131, conductor 144, verticalswitch-Wiper" 103, contact-point 117, conductor 123, .vertical-rnagnet 144 (Fig. 2), conductor 1 16 to battery 11 and to ground. The closure of this circuit results, of course, in the sending of one impulse through vertical-magnet 14 1 causing the latter to raise the shaft of switch K one stop. The switch-wiper 35, of course, passes onto contact 132, Where it again closes a circuit, and sends another impulse though vertical-magnet 144: of the said preliminary-connectorswitch K. This latter circuit is from ground through wiper contacopoint 132, conductor 136*. contact-point 1 17, contact-arm 140, conductor 135, conductors 1 1 1 and 128, verticalswitch-Wiper 103, contact-point 117, thence through conductor 123 to vertical-magnet 1 11'" of the switch K a-ndto battery. At such time, the. spring-wiper 35 passes on to contact-point 133, where it effects the transmission of another impulse through verti- -al-magnct 1-14, the circuit at this time being closed through contact-point 133, conductoi-"137, c011tact-point 118, armature 1'11, contact-point 1+7, armature 1-10, conductor 135, contact-point 131, conductors 1 11 and 128 to vertical-wiper 103, etc., as before. In this way, and as wiper 35 passes on to contact-pint 13-1. another electrical impulse is transmitted through vertical-niagnet 1-11; and this time the circuit includes the contact-point 134-, conductor 131', contactpoint 11-0, ari'nature 142, contact-point 11-8, armature 1-11, contact 1 1-7, armature. 110, conductors 135, 1-14 and 128, verticalwiper 103, etc. The spring viper 35 moves onto contact-point 135, where it again at fects the transmission of an electrical iinpulse through contact-point 135, conductor 1.39, contact-point .150, armature 1 13, contact-point 119, armature 1-12, contact-point 118, armature 141, contact-point 1-17, armature 140, conductors 1355 144; and 128, vertical-Wiper 103, ctc. -;-:it being understood that from this point on" eachcircuitthrough the vertical-magnet 14-11 is the same as the others. As stated, spi'i11g-\\-'ipc1' 35 moves into contact with the switch-point 136; but from this point it will not, and cannot, effect the transmission of another vertical impulse through the vertical-mag net 141 1. This, of course, is due to the factthat armature 13 of coil is, at such time, drawn up, thereby breaking contact with contact-p0int 28, so that springqii'pcr will then and from there be incapable of offecting the transmission of further vertical impulses, and will cause the transmission of no impulse or impulses of any kind what-ever until it passes from contact-point 137 onto contact-point 138; and when this happens it will commence to send rotary impulses over the rotary-line to the rotary-magnet 145 of the preliminar -connector-switch K.

It will now be seen that five impulses, corresponding to the first digit of the number of the calling sul'iscriber, have now been transmitted through vertical-magnetl 1 14; of the preliminary-connector-switch K, thus raising the wipers of this preliminaryconnector to the proper le\-'els--that is to say, the points where these wipers will be opposite the fifth row of contact-teeth, and thus made ready for entering their levels as soon as rotary impulses are sent through the said rotary-magnet of the switch: and it will be seen that-a rotary impulse is transmitted as soon as the spring-wiper reaches contact-point 138, a circuit being thereby momentarily closed as follows:

From ground through contact-arm 02,, contact-arm 32), conductor 13-1, spring-wiper 35, contact-point 138, conductor 127, 'otarywiper 102 of the switch-operating machine, contact'point 113, conductor 122, rotaryinagnet 1e15, conductor 1% to battery 11 and to ground; thus causing a single rotary impulse to be sent through the rotarymagnet 1-15, the construction of which lat ter is, as will hereinafter more fully appear, such that it causes the switch-shaft of the preliininary-conncctoi" to make one rotary step, thus causing the shaft-wipers 151 and 152 to be brought into contact with the switch-points 154 and 153 of the bank of contacts allotted to this switch; and also causing private-wiper 155 to be placed in electrical contact with the tooth or contactpoint 156 of the so-called private-bank of this switch. At this time, it will be seen that. the preliininary-connector-switch K has completed its operation, having placed the line-wipers 151 and 152 on the l'irst setof contacts of the fifth row or level in the bank of line-contacts, it being ob served that this bank is made up of pairs of contacts, each pair consisting of two contacts connected with the opposite sides of a subscribers line. In. other words, connec tion is made with the set of contacts which correspond to the number of the calling subscriber, thus completing the connection from the lines coming in from telephone 51 through conductors 157 and 158, line-Wipers 151 and 152 to trunk-line-conductors leading to a regular first selectonswitch, or, as shown in Fig. 15, to an ordinary connector-switch, or to any other suitable switching apparatus. At this time, it will be seen that a circuit is also established throu h the bridge-cut-oil -relay 159 (Fig. 2), this circuit being from ground through private-wiper 155, oontact-point 156, through relay-coil 159 to battery 11 and to ground; thus causing the core of coil 159 to attract the armature 159 and efi'ccting the retention of this armature in its attracted position until the preliminary-connectorswitch K is finally released and restored to its normal condition, after the conversation has been terminated. When the bridgo-cutoff-relay 159 attracts its ar1natureit being understood that one of these bridge-cuneifrelays can be allotted to and made individual to each subscribers lineit breaks contact between the switch-springs or contacts 8, 9 and 10, thus opening the bridge normally closed across the line-conductors 1 and 2 leading from telephone 51, and which bridge includes the line-relay coils or windings 6 and 7 connected normally to battery through the said contact-arnisg and this leaves the line of the calling subscriber free from bridges of this character, and puts the line in condition for subscriber 51 to operate the regular first selector, second selector, third selector, etc, and the regular and usual connector; or, as stated, the calling subscriber may then simply operate a conhector-switch, as shown in Fig. 15, and secure direct connection with the line of the called subscriber without usin any selectors whatever. it will also is seen that the wiper 35, after leaving contact-point 138, passes on, in the manner previously described, until it again returns to contactpoint 100; and at the same time cam 34 also returns to its original position, thus pressing contact-arm 21 away from contact-arm and into engagement with contact-arm 2st, and also breaking contact between the arms 23 and 22. Qbviously, with the arrangement shown, the contact 21, as it breaks away from the arm 20, serves to open the previously described circuit from ground to coils 36 and 37, and all of these coils in series, as shown in Fig. 1; and this action having been accomplished, armature 14 returns, of course, to its original position in engagement with the contact-point 27, while armature 13 of coil 15 returns to its original position in engagement with contact-point 28. It will be seen, however, that this circuit also includes the relay-coil 25 and, consequently, that the latter releases its armature, thereby breaking contact between contact-arm 29 and contact-point 30, and in this way opening the circuit from ground through rotary-magnet-coil 31. This, of course, results in bringing the wiper to rest on contact-point 100, where it remains until a new call is sent in from any other telephone of this particular group of subscribers, or from anyother subscriber in the exchange, providing the size of the exchange is of a character indicated in the drawings. It must be borne in mind, however, that another circuit is broken or opened up-- that is to say, the circuit through rotaryrnagnet 104owing to the separation of contacts 22 and 23; and consequently inagnet 104 releases its armature, whereupon the pawl of armature 107 engages the shaft carrying the spring-wipers 101, 102 and 108, and thus moves the latter into engagement with the points 110, 11s and 118, ready to receive the next call coming in from the calling wiper 35 in response to the removal oi? a telephone-receiver from its book by some other subscriber, or in response to cur rent transmitted in any other suitable manner for the purpose of bringing about the connecting. operations which are of a more or less preliminary character, and which must take place before the electrical impulses representing the digits of the called number are permitted to flow through the relays or magnets of a selector-switch or conncctorswitch, or both, as the case may be.

The method of calling the desired number Y and 1,57, and

maybe as follows: In Fig. 14 the connectormechanism is shown, and in Fig. 15 this connector is shown in use between the two subscribers stations. After subscriber 51 has, in the manner previously explained, obtained connection with the trunk-line L leading to the idle connector-switch, the calling subscriber then operates his calling device, such, for example, as the keys or buttons a" and (1."; it luring understood, of course, that in practicithe calling device may be of any suitable, known or approved construction, and that the said keys or butions are simply shown as a matter of convenience of illustration. l/Vhenthe key or button a. is pressed, it is obvious that the line-conductor 2 will be connected through contact-point a, conductors a and (1 ,0011- tacts a and a, to ground at a and in a similar manner, when the key or button a" is pressed, the line conductor 1 is connected to ground through contact a and thence through the same conducting path just described in connection with the grounding of lineconductor 1. In Fig. A repre sents the apparatus of the calling subscriber, and B that of the called subscriln'er. The

heavy lines represent the talking circuitthat is to say, the circuits for" the voice currents. The relays and other devices included between the broken lines 1'1 and belong m the preliminaryronnector in use between the two subscribers" lines. The relays, magnets and switching devices etc, included between the broken lines 2-2 and 3-3 belong to the connectorwhich is shown in use between the two lines. The devices shown at the left of line 1-1 are individual to the calling subscribers line. In a similar manner, the devices shown at the right of line 3 -3 are individual to the line of the called subscriber. lithe number of the called subscriber is 99, the calling subscriber will first press. the switch-key a? nine times, thereby sending nine distinct impulses over the vertical line-conductors 1 through the vertical-relay m by reason. of the 'connection thus brought about between the conductor Z and the ground at a and the said relay and the non-grounded pole of battery 11 throu 'h the medium of suitable conductors, as shown, for example, in Fig. 15. The vertical-relay which includes the battery 11, the verticalmagnet m, sideswitch-wipencontrct m, wiper m contact-springs m and m, and contactvsprings m and m to ground at m and back tobattery. The first impulse releases the lo'cking-dogs of the connector, because the hook m? lifts the re lease-link m ofi the pin m",land the nine distinct impulses cause" the shaft to be stepped up to the ninth level of bank-con tacts, thus bringing the private-,-"verbeen limited. the first time by the engage.-

in turn closes the circuit nine times,

tical and rotary shaft-wipers into the desired position. The calling subscriber then presses the switch-key a once, so as to ground the rotary-line-conductoi" butonce, thus sending a- .single lll'lPlllSGlihlOUgh the private-magnet m of the connector. This ma net, when energized-and then dcenergize permits the finger m to escape one tooth, under the influence of the spring m and to thereby shift the side-switch wifiiers from first to second position. The ca ing subscriber 'then again presses the switch-key a." nine times, so as to send nine distinct impulses over the vertical-lineconductor Z; but this time, owing to the shifting of the-wiper 'm? onto the contact m, the said impulses energize the rotarymagnet an owing to the circuit arrangement provided and illustrated in Fig. 14. The nine rotary impulses thus given the shaft m of the connector by the said rotary-magnet bring the wipers m m and m into the desired position-that is to say, into correct position for-making connection with the line and private normals connecting with the line of the called subscriber, .as shown in Fig. 15.. After this, the

calling subscriber again presses the switchkey a once, and thereby again energizes and tie-energizes the private-magnet m of the connector. The said private-mag, net permits the finger an to escape. and move outwardly until it strikes the stop m the movement of this side-switch having.

ment of the projection m with the cam m. The final operation of the side swit -:l1, in this manner, moves the sideswitch-wipers?" from second position tothird position, thus connecting the line-conductors L with the-conductors leading to the"vertical and rotaryhwipers m and m which latter are now in engagement with the bankcontacts connected with the line-normals leading to the line of the c'alled'subscriber. The final action of the side-switch in this manner also makes it possible, by pressing .the key a, to connect the ground a with,

the vertical-dine conductor lot the calling subsoribefls line, and tothereby throw ring- 1 ing current onto the completed line-circuit, between the two subscribers by reason of the" engagement of the wiper m with the third contact m. When the calling subscriber presses the ringing-key in this manner, av circuit is formed from ground, .as stated, through the. conductors 1 and 157, through the vertical-line-relay m to battery 5 1L,

- and then to ground; and this will,=of course,

bring the springs m and m together, thereby closing a circuit from round on through springs m and m, t rough the wiper -m, through the ringing-relay m 7 and thence to the non-grounded pole of the The ringing-relay thus energized 

